This invention relates to a personal monitoring device arranged to provide an alarm signal in the absence of physical movements by the user of the device.
Various forms of such devices have been previously proposed, for example, as described in U.K. Pat. Nos. 919765, 1226478, 1514897 and 1547364 and U.S. Pat. Nos. 3,163,856, 3,614,763, 3,740,648 and 4,110,741 but these devices all suffer from the disadvantage that the basic transducer which senses the physical activity limits the usefulness of the device. For example some of these known transducers utilise a mercury switch whilst others utilise a pendulum switch both of which only function correctly, or at all, when orientated in a particular manner. U.K. Pat. No. 1514897 and U.S. Pat No. 4,110,741 both disclose a transducer in the form of a vibratory member carrying a piezo-resistant gauge which provides a continuously variable output without discrimination in relation to the source of vibration. Such discrimination is provided by a band-pass filter with a preset bandwidth.
The present invention is concerned with an improved form of device for monitoring physical activity of persons incorporating an improved form of transducer.
The invention is particularly useful to users involved in the fire and rescue services where hazardous areas are encountered so that in the event of a user becoming physically inactive, for example, due to becoming overpowered by noxious gases, an alarm signal will be emitted which can be detected by personnel outside the hazardous area who can thereby be warned to take action to assist the user of the device.